1. Field of the Invention
The present invention relates to a solvent delivery device and a liquid chromatograph such as a high-performance liquid chromatograph (HPLC) and an ultra high-performance liquid chromatograph (UHPLC) for transferring a sample, injected into an analytical flow path by mobile phases sent by the solvent delivery device, to an analytical column, separating the sample into components, and detecting the respective separated components.
2. Description of the Related Art
As a solvent delivery device for sending mobile phases for transferring a sample, injected into an analytical flow path having an analytical column and a detector, to the analytical column and the detector, a gradient solvent delivery device is used in some cases. The gradient solvent delivery device is for sending the solution in the analytical flow path while changing composition of a mixed solution of a plurality of kinds of mobile phases with time (see Japanese Patent Application Laid-Open No. 2002-14084).
A structure of a liquid chromatograph including a low-pressure gradient solvent delivery device will be described by using FIG. 4.
The solvent delivery device 30 for supplying mobile phases to an analytical flow path 4 is provided and a sample injecting section 6, an analytical column 8, and a detector 10 are disposed on the analytical flow path 4. The sample injected by the sample injecting section 6 into the analytical flow path 4 is introduced into the analytical column 8 by the mobile phases sent by the solvent delivery device 30 and separated into respective components. The sample components separated in the analytical column 8 are transferred by the mobile phases to the detector 10 and detected.
The solvent delivery device 30 includes a solvent delivery pump 12 disposed on the analytical flow path 4 and a flow path switching valve 14 for switching between kinds of mobile phases pumped up by the solvent delivery pump 12. The flow path switching valve 14 includes four selective ports a to d disposed at a periphery portion and a central port disposed at a central portion and is formed to selectively connect any one of the selective ports to the central port. The analytical flow path 4 is connected to the central port of the flow path switching valve 14 and mobile phase sending flow paths 32, 34, 36, and 38 are respectively connected to the selective ports a, b, c, and d. The mobile phase sending flow paths 32, 34, 36, and 38 are flow paths for respectively sending liquid phases A, B, C, and D and a degasser 24 for degassing the mobile phases is provided on the flow paths 32, 34, 36, and 38.
The flow path switching valve 14 switches the flow path to be connected to the solvent delivery pump 12 according to time to thereby change composition of the mobile phase to be sent through the analytical flow path 4 by the solvent delivery pump 12.
In the conventional gradient solvent delivery device shown in FIG. 4, when the analysis ends and the solvent delivery pump 12 stops, the mobile phases remain in each flow path 32, 34, 36, and 38. For example, if the liquid phase A is an organic solvent and the liquid phase B is a high concentration buffer solution and when the mobile phases remain in the respective flow paths 32 and 34 after the end of the analysis, salt is liable to be precipitated at meeting portions of the flow paths in the flow path switching valve 14. If the salt is precipitated in the flow path switching valve 14, the flow paths are clogged to cause liquid leakage or the salt is pinched between a valve seat and a valve element of a solenoid valve forming the flow path switching valve 14 to cause failure of the solenoid valve.